1. Field of the Invention
The present invention relates to a device for needling a fibrous web.
2. Description of Related Art
For consolidating and structuring laid fibrous webs, it is known from the prior art to pierce the fibrous webs with a plurality of needles, which are guided in an oscillating upward and downward movement. Since the needles are not smooth but provided with barbed hooks that are open in the piercing direction, individual fibers of the fibrous web are caught and realigned within the fibrous web when the needles pierce the latter. This results in the desired fiber-mingling and bonding effects within the fibrous web. For guiding the plurality of needles, devices are used in which the needles are disposed on a lower side of a needle beam. The needle beam is held with the aid of a movable beam carrier, which is driven by means of a vertical drive for an oscillating vertical movement. In order to enable the straightest possible insertion of the needles into the fibrous web during the vertical movement, it is further known from the prior art to use a guiding device, which acts on the beam carrier and which guides the vertical movement of the beam carrier.
A device for needling a fibrous web is thus disclosed in DE 44 31 055 A1, in which device the guiding device is formed by a rocker, one end of which is held on a machine frame with the aid of a rotary bearing and the opposite free end of which is coupled to the beam carrier via a swivel joint. The beam carrier is thus guided on a guideway predetermined by the rocker. The guideway of the beam carrier is shaped like a circular arc. In order to still produce defined punctures with the help of the needles, curved needles are used that are adapted to the guideway of the beam carrier.
U.S. Pat. No. 4,241,479 discloses another device for needling a fibrous web, in which device the guiding device for the straight guidance of the beam carrier is formed by two rockers that are held in supporting bearings in relation to a machine frame. The supporting bearings each comprise at least one tooth gap, in which that end of the rocker that is formed as a tooth engages. The device disclosed thus requires more space in order to be able to guide the outwardly protruding rockers in the machine frame. Furthermore, the lubrication and sealing of the teeth disposed between the rockers and the supporting bearings pose problems, in particular.
EP 0 364 105 A1 discloses another device for needling a fibrous web, in which device the guiding device comprises at least one guiding rod that is guided in a guide bushing held on a machine frame. One free end of the guiding rod is connected to the beam carrier so that the beam carrier maintains a guideway predetermined by the guiding rod and the guide bushing during the vertical movement. The device disclosed is also based on a tribological pairing of two parts for guiding the beam carrier, and the lubrication and sealing of these parts pose problems, in particular, and require a large amount of equipment.
Moreover, the guiding devices for the straight guidance of the beam carrier known from the prior art only allow the needle beam to be driven in the vertical direction. Retrofits of the known devices for carrying out a horizontal movement of the beam carrier are either not feasible or are associated with considerable expenditure.